Kidney Function Biomarkers

Kidney Function Biomarkers

Creatinine

• Definition: A waste product of muscle metabolism, produced at a constant rate
• Measurement: Serum creatinine level, usually reported in mg/dL or μmol/L
• Significance: Elevated levels indicate kidney dysfunction or kidney disease
• Limitations: Muscle mass, diet, and certain medications can affect creatinine levels

Urea (Blood Urea Nitrogen, BUN)

• Definition: A waste product of protein metabolism, produced in the liver and excreted by the kidneys
• Measurement: Serum urea level, usually reported in mg/dL or mmol/L
• Significance: Elevated levels indicate kidney dysfunction or kidney disease
• Limitations: Dehydration, heart failure, and gastrointestinal bleeding can affect urea levels

Cystatin C

• Definition: A cysteine protease inhibitor produced by all nucleated cells
• Measurement: Serum cystatin C level, usually reported in mg/L or mg/mL
• Significance: Elevated levels indicate kidney dysfunction or kidney disease, more sensitive than creatinine
• Advantages: Less affected by muscle mass, diet, and certain medications compared to creatinine

Neutrophil Gelatinase-Associated Lipocalin (NGAL)

• Definition: A protein produced by neutrophils and epithelial cells in response to kidney injury
• Measurement: Urine or serum NGAL level, usually reported in ng/mL
• Significance: Elevated levels indicate acute kidney injury (AKI) or chronic kidney disease (CKD)
• Advantages: Early biomarker for AKI, may predict CKD progression

Microalbuminuria

• Definition: A small amount of albumin in the urine, indicating glomerular damage
• Measurement: Urine albumin-to-creatinine ratio (UACR), usually reported in mg/g
• Significance: Elevated levels indicate early kidney damage, predictive of CKD progression
• Significance in Diabetes: Microalbuminuria is a hallmark of diabetic nephropathy

Kidney Function Biomarkers

Creatinine

• A waste product of muscle metabolism, produced at a constant rate
• Measured in serum, usually reported in mg/dL or μmol/L
• Elevated levels indicate kidney dysfunction or kidney disease
• Muscle mass, diet, and certain medications can affect creatinine levels

Urea (Blood Urea Nitrogen, BUN)

• A waste product of protein metabolism, produced in the liver and excreted by the kidneys
• Measured in serum, usually reported in mg/dL or mmol/L
• Elevated levels indicate kidney dysfunction or kidney disease
• Dehydration, heart failure, and gastrointestinal bleeding can affect urea levels

Cystatin C

• A cysteine protease inhibitor produced by all nucleated cells
• Measured in serum, usually reported in mg/L or mg/mL
• Elevated levels indicate kidney dysfunction or kidney disease, more sensitive than creatinine
• Less affected by muscle mass, diet, and certain medications compared to creatinine

Neutrophil Gelatinase-Associated Lipocalin (NGAL)

• A protein produced by neutrophils and epithelial cells in response to kidney injury
• Measured in urine or serum, usually reported in ng/mL
• Elevated levels indicate acute kidney injury (AKI) or chronic kidney disease (CKD)
• Early biomarker for AKI, may predict CKD progression

Microalbuminuria

• A small amount of albumin in the urine, indicating glomerular damage
• Measured in urine albumin-to-creatinine ratio (UACR), usually reported in mg/g
• Elevated levels indicate early kidney damage, predictive of CKD progression
• In diabetes, microalbuminuria is a hallmark of diabetic nephropathy